Clydesdale,heavy draft-horse breed that originated in Lanarkshire, Scotland, near the River Clyde. The breed was improved about 1715 by mating a Flemish stallion with local mares; Shire blood was later introduced. Clydesdales were taken to North America about 1842 but never became a popular draft horse there.

The Clydesdale averages 17 to 18 hands (68 to 72 inches [173 to 183 cm]) tall and 2,000 pounds (900 kg) in weight. The colour is usually bay, dark brown, or black, with prominent white markings. Noted for its high leg action while walking or trotting, the breed is characterized by feather (long hair) on the legs, attractive heads, and well-formed legs and feet.

The British breed association is the Clydesdale Horse Society of Great Britain and Ireland, organized in 1877. The American Clydesdale Horse Association, organized in 1879, was later succeeded by the Clydesdale Breeders of the United States.

See the Table of Selected Breeds of Heavy Horses for further information.